It is known that polyesters prepared by the polycondensation of a dihydric alcohol and a dicarboxylic acid are excellent fiber forming or moldable polymers. Commercially, the most important polyesters are those prepared by the condensation of terephthalic acid or dimethylterephthalate and a polymethylene glycol containing from 2 to 10 carbon atoms, and more particularly ethylene glycol, 1,4-cyclohexanedimethanol, or mixtures thereof. These polyesters are relatively inert and hydrophobic materials which are capable of being formed into filaments which can be drawn to produce textile fibers or plastics of superior strength and pliability.
Unfortunately, native polyester fibers and plastics as manufactured generally have an undesirable yellow appearance. At present, in order to improve the apparent whiteness of polyester fibers or neutral color characteristics of polyester plastics, certain so-called toners are incorporated into the polyester to hide or offset the yellow color. Typically, such toners usually have a visible absorption maximum in the range about 575 nm to 595 nm as measured in acetone.
Cobalt acetate is one of the most widely used toners in the industry to mask the yellow color of polymers. However, cobalt acetate has a number of noteworthy disadvantages. For example, cobalt acetate toned materials tend to be unstable during storage and are particularly susceptible to temperature and humidity, and undergo an undesirable color shift toward yellow. Further, when high cobalt concentrations are needed to mask the yellow color of some polymers there is a tendency to impart a gray color to the polymer.
Another disadvantage in the use of cobalt acetate is the limitations set by various governmental agencies in the level of cobalt deemed allowable in polyester catalyst systems.
Further, cobalt salts tend to lower the resulting polymer's thermal stability and increases acetaldehyde formation in poly(ethylene terephthalate).
Lastly, cobalt has a strong tendency to form insoluble residues in manufacturing process equipment, thereby leading to manufacturing quality control problems.
In U.S. Pat. No. 4,745,174, incorporated herein by reference, certain 1-cyano-3H-dibenz-[f,ij]isoquinoline-2,7-dione compounds were disclosed which overcome many of the disadvantages of cobalt acetate as a toner for polyesters while also being stable under the conditions of polymerization and melt processing. These compounds are also stable to light and to other environmental conditions to which fibers and plastics may be exposed and do not deleteriously affect the overall physical properties of the fibers or plastics.
These compounds correspond to the following structure formula I: ##STR1## wherein R is hydrogen, cycloalkyl, allyl, alkyl, aralkyl, alkoxyalkyl or cycloalkylalkylene;
R.sub.1 is hydrogen, halogen, alkyl, alkoxy, aryloxy, alkylthio, or arylthio; PA1 R.sub.2 is hydrogen, alkyl, aryl, alkoxy, arylalkoxy, alkylthio, arylthio, carbalkoxy, carbaralkoxy, carboxy, sulfamoyl, alkylsulfamoyl, dialkylsulfamoyl, alkylarylsulfamoyl, cycloalkylsulfamoyl, arylsulfamoyl, carbamoyl, alkylcarbamoyl, dialkylcarbamoyl, alkylarylcarbamoyl, cycloalkylcarbamoyl, arylcarbamoyl, 2-pyrrolidono, acylamido or N-alkylacylamido; PA1 R.sub.3 is one or more residues selected from the group consisting of hydrogen, halogen, alkyl and alkoxy; and PA1 n is an integer of 1 to 5;
wherein one or more alkyl, alkoxy, aryl, aryloxy, alkylthio, arylthio or aralkyl groups may contain one or more reactive residues selected from the group consisting of carboxy, carbalkoxy, carbaryloxy, N-alkylcarbamoyloxy, carbamoyloxy, acyloxy, chlorocarbonyl, hydroxyl, cycloalkylcarbonyloxy, N-arylcarbamoyloxy and N,N-dialkylcarbamoyloxy, wherein said alkyl and aryl groups may further contain substituents such as alkoxy, acyloxy, halogen, cyano, hydroxy and acylamido.
The disclosed process for preparing compounds of formula (I) consisted of reacting an intermediate 1-amino-4-haloanthraquinone (II) with chloroacetyl chloride or chloroacetic anhydride to give 1-(chloroacetamido-4-halogenoanthraquinones (III), which were then ##STR2## treated with an alkali metal cyanide such as potassium cyanide or sodium cyanide (see also, Allen, C. F. H, et al., JACS (January, 1950), 585-88) to give the 1-cyano-6-halogeno-3H-dibenz[f,ij] isoquinoline -2,7-dione intermediate (IV), which was reacted with anilines by a modified Ullman reaction involving nitrogen arylation of said anilines in the presence of copper catalysts as shown below: ##STR3## to give desired compounds of formula (I).
Recent experience has shown the presently known process described above to present many difficulties and problems, including low yields, poor quality, toxicity and safety hazards, environmental concerns over the disposal of reaction by-products, and consequent poor economic yield. First, the use of chloroacetyl chloride or chloroacetic anhydride presents difficulties with regard to safety because of their lachrymatory and toxiological properties. Also, the conversion of (III) into (IV) requires the use of sodium cyanide or potassium cyanide and is very solvent dependent, with the only two known useful solvents being acetonitrile or 2-hydroxyethyl acetate. Acetonitrile is very toxic and volatile and disposal of the acetonitrile/cyanide wastes creates major environmental problems. Another potential solvent, 2-hydroxyethyl acetate, is expensive and the handling and disposal thereof present toxicological and environmental concerns as well. Of even more critical concern are the low yields and poor quality of intermediate compounds (IV) and the blue toners (I) prepared therefrom, which must be repeatedly recrystallized from hazardous high boiling solvents such as nitrobenzene to remove undesirable impurities thereby resulting in a very low yield of usable blue toners (I) (see U.S. Pat. No. 4,745,174 and Comparative Example 3 herein). It has also been found that the quality and purity of toners (I) vary greatly giving blue toners which are not consistent in their degree of redness or greenness in color, thus seriously limiting their effectiveness as toners.